Home›Pool Types›Infinity Pools (Rim-Flow)
An infinity pool — what the South African trade calls a rim-flow pool — is a pool whose water spills over a precisely level edge into a hidden tank below, so the surface reads as though it has no boundary.
What is a rim-flow pool?
An infinity pool is built so that water runs continuously over one or more of its edges, disappearing over a lip set exactly level so the surface looks as though it has no boundary. The water is not lost: it falls into a catch basin or a channel, drains to a hidden balance tank, and a second pump returns it. In South Africa the trade term is rim-flow; buyers also search vanishing edge, negative edge and wet edge.
Two different pools sit under those names. A single-sided vanishing edge spills over one wall, usually towards a view, into a basin below. A full perimeter overflow — knife-edge or deck-level — spills over every side into a slot flush with the paving, so the water reads level with the deck rather than the horizon. They need different engineering, different tank sizing and different money.
Underneath the edge, a rim-flow pool is a concrete pool: the shell has to be formed on site to carry a lip level to within millimetres.
Award-winning South African rim-flow pools
Every pool below won an NSPI award in a rim-flow category. Each links to the project and to the builder who built it.
Platinum
A rectangular pool set between clipped parterre beds, with a curved spa corner built into the near end.
Built by Robust Pools and Paving — NSPI Platinum 2025 KwaZulu-Natal
Gold
A clifftop pool on the KwaZulu-Natal coast, its edge running out towards the rocks and the beach below.
Built by Kenny Matthews Pools cc — NSPI Gold 2025 KwaZulu-Natal
Gold
Water held level against a raised concrete wall, with lawn and terraced steps rising behind it.
Built by Radiant Pools — NSPI Gold 2025 Western Cape
Gold
A glass-sided pool cantilevered above a Johannesburg courtyard development.
Built by Curtis Pools — NSPI Gold 2014 Gauteng
Gold
The edge dissolving towards a Cape lagoon, with a dark sculptural chimney anchoring the terrace.
Built by Island Pools — NSPI Gold 2025 Western Cape
Gold
Turquoise water carried out over a lower terrace, the house stepping back behind it.
Built by Horizon Pools (Pty) Ltd — NSPI Gold 2014 Western CapeHow it's built
Where the edge goes is a design decision and a structural one at once: a raised weir wall on a slope is a retaining element with water on one side and nothing on the other. Ask in writing what engineering input the design carries — no published South African standard we found sets a certification requirement for pool structures. Plans go to your municipality as with any pool.
The hole is opened and, on a slope, the ground below the edge is retained and drained before anything is built on it — this is where the money goes on a view site. The shell is then built as on any concrete pool, but with the weir wall detailed as the structural element it is.
The stage that decides whether the pool works. The lip must be level along its whole length: the American designer-education body GENESIS recommends building vanishing edges to within about 1.6 mm, and no South African source publishes a tolerance at all. Its shape matters too — a sharper edge needs less water to look right.
A single-sided edge spills into a basin below the wall, a perimeter overflow into a channel around the deck. Either drains to a balance tank that must hold everything in transit over the edge, plus surge, plus wind and evaporation reserve — and it has to stay accessible.
A second, dedicated pump lifts water from the tank back to the edge, sized on the length of the lip rather than the volume of the pool. A check valve stops the pool draining back through the tank when that pump is off, and the tank must keep enough depth over its suction that it cannot pull air.
Rim-flow pools are usually fully tiled rather than plastered, and South African specialists commonly double-waterproof them. The visible face of the weir wall is a finish decision in itself — tiled, mosaic, stone-clad, or a glass panel.
Fill, balance, then run the edge and look at it. An even sheet along the whole lip is the acceptance test, and a low spot shows immediately as a dry patch. Agree beforehand what happens if it is not right — correcting a lip after tiling is expensive.
Cost guide
| Tier | Range (ZAR) | What that typically includes |
|---|---|---|
| Single-sided rim-flow, straightforward site | R500,000 – R750,000 | A concrete pool of ordinary family size with a vanishing edge on one wall: tiled spill lip, catch basin, balance tank, second pump and its plumbing. A level or gently sloping site with machine access. Excludes paving, decking, fencing and heating. |
| Single-sided rim-flow on a slope | R750,000 – R1,200,000 | The same pool where the view actually is. Adds a raised weir wall, retaining and structural engineering, a plant room, a larger tank, automation and a fully tiled or clad weir face. Where most South African rim-flow projects sit. |
| Perimeter overflow, or a glass edge | R1,200,000 and up | A knife-edge or deck-level pool spilling on all sides into a channel flush with the paving, or an edge built with a glass panel. More edge, a bigger tank, tolerance to hold around a closed loop, and architect and engineer involvement throughout. |
Prices last reviewed 8 August 2026.
What buyers actually want to know is what the edge costs on top of a normal pool. No South African source answers it — and none, on any pool type, says whether its figures include VAT, worth roughly R100,000 on a R750,000 pool. What can be said honestly, as of August 2026:
The honest picture
The reason the type exists. A level lip takes away the visual boundary between the water and what lies behind it, so the pool reads as continuous with the view — or, on a deck-level pool, with the paving.
A fall across the property is a problem for most pools and the whole point of this one. The slope that forces retaining and engineering is what gives the edge something to disappear over.
Water exits across the full length of the lip rather than through a single skimmer box, so what is floating on the surface goes with it.
Which means concrete's freedom: any shape, any depth, built into slopes and tight sites, on a shell with a structural life measured in decades.
The perimeter-overflow version puts the water at the height of the surrounding deck — which is why South African builders describe the appeal as symmetry between surrounds and water rather than as a view effect.
Level to within millimetres along its whole length, and a low spot shows as a dry section of the sheet.
Mitigation: Choose a builder with finished rim-flow work you can go and stand in front of, ask what tolerance they build to, and agree the acceptance test before the first fill.
When the power goes off the edge stops, the water in transit drains down, and the tank sits full until the pump runs again.
Mitigation: A check valve to stop water siphoning back, a timer with battery backup, and a basin sized to take everything that drains into it.
A spilling surface evaporates faster than a flat one, and wind carries part of the sheet away.
Mitigation: Design the basin for the prevailing wind, cover the pool, and plan the top-up honestly — particularly in Cape Town.
A second pump feeding the edge is a second monthly electricity line.
Mitigation: A variable-speed pump on that circuit, and running the edge for part of the day, which also limits scale on the weir face.
The visible wall is wet, then dry, then wet again — the condition that leaves scale and staining, in full view.
Mitigation: Keep the water balanced, and specify a finish you can live with as it weathers.
How it compares
The parent, not the rival. Essentially every rim-flow pool in South Africa is a concrete pool: the shell must be formed on site to carry a lip level to within millimetres, and the weir wall is a structural element in its own right. If you are choosing a rim-flow edge you are choosing a concrete pool — read the concrete pools guide for the shell, the finish and the timeline.
A moulded shell rarely gives a true rim-flow edge, and the reason is mechanical rather than a shortcoming: the rim is formed in the factory, so its levelness is set by the mould and the bedding, where a sprayed or poured wall is built and trimmed on site until the lip is right. Where the two are combined internationally, the edge structure and catch basin are built separately around the shell. Fibreglass remains the faster, smoother-surfaced route to a conventional pool.
A use case rather than a construction method, and a common partner for a rim-flow edge: a long narrow pool has a long straight wall, the easiest lip to build level and the most striking end-on.
A finish rather than a structure, and the one most often specified here. Rim-flow pools are commonly fully tiled rather than plastered, and the weir face is the wall a mosaic finish is made for.
Maintenance & running costs
A rim-flow pool asks for everything a concrete pool asks for, plus three things of its own: a second pump circuit to power and pay for, a balance tank whose level has to be managed, and a weir face that shows every mark. Budget above the R1,200–R2,000 a month a family-sized South African pool costs to run as of August 2026.
When the pump stops, a rim-flow pool stops being a rim-flow pool. The edge goes dry, the water in transit drains into the basin and the balance tank, and the tank sits full until the pump runs again. That much is cosmetic. What is not cosmetic is what happens if the system was not built for it: without a check valve on the line from the basin, water can siphon backwards out of the pool, and a basin and tank sized only for normal running will overflow and discharge whatever they cannot hold — water, and the chemicals in it. There is a documented case of exactly that, twice in under two months, on a pool with no backflow prevention.
So ask two questions: is there a check valve preventing back-siphoning when the edge pump is off, and can the basin and tank take a full drain-down? Then run the pumps on a timer with battery backup, because an outage silently resets a schedule and a rim-flow pool left off is one with a dry edge and a full tank. Eskom's April 2026 outlook forecast no load-shedding through the April-to-August winter, but municipal outages have not gone away.
At the 2026 working rate of R4.00/kWh, a 1.1 kW filtration pump running six hours a day is around R790 a month, and a second 0.75 kW variable-speed pump on the edge circuit adds roughly R540 a month — our own arithmetic (kW × hours × 30 × R4.00), because no South African source publishes a running cost for an edge pump. Running the edge a few hours rather than all day is the obvious lever.
A spilling edge loses more water than a still surface: moving water presents more surface to the air, and wind carries part of a thin sheet clear of the basin. The one international design calculator we found allows roughly 50% more evaporation reserve for a vanishing edge than for a deck-level slot — the honest shape of the difference, since nobody publishes litres per day for a South African rim-flow pool. A South African supplier put general pool evaporation at 35–45 mm a week in summer, and a cover at 90–95% effective against it.
Then the collision nobody in the industry appears to have addressed. Cape Town's permanent water regulations — permanent, not tied to a restriction level — require a pool to be covered when not in use, and state that automatic top-up systems using a float valve fed from a municipal drinking water source are not allowed. A rim-flow pool is designed around a balance tank that needs topping up, and international practice for this type assumes automatic top-up as standard. We could find nothing from the City, from any South African builder or from any industry body addressing a balance-tank pool under these rules. One thing is worth noticing, and it is not a workaround: the regulation names a float valve fed from municipal drinking water, where international balance-tank design uses electronic level control with a solenoid valve. If you are building a rim-flow pool in Cape Town, put the question to the City in writing before you design around automatic top-up.
Wind is a design input here, not a nuisance. International guidance is to size the catch basin for the height of the drop and the wind the site actually gets — the rule of thumb is a basin about as wide as the weir wall is tall — and to design for the prevailing direction. Get it wrong and the sheet blows past the basin and down the slope. Cape Town's mean wind runs from about 3 m/s in the calm months to about 6 m/s in January, so an exposed Cape view site is not a still-air site. At the coast, specify 316 marine-grade stainless for rails and fixings. On a slope, international pool engineering holds that a pool near the top of a fall must be designed so its walls carry the water without relying on the soil behind them — no published South African standard surfaced in our research, so treat it as a question for your engineer rather than an absence of a requirement.
Questions buyers actually ask
An infinity pool is one whose water runs over a precisely level edge into a hidden tank and is pumped back, so the surface looks as if it has no boundary. “Rim-flow” is the South African trade name for the same idea; you will also see “vanishing edge”, “negative edge” and “wet edge”. One caution: South African builders use “rim-flow” for both a single-sided edge and a full perimeter overflow, so say which you mean — they write “double-sided rimflow” for exactly that reason.
As of August 2026, expect one to start roughly where a good conventional concrete pool ends — from about R500,000, with most projects between R500,000 and R1,200,000 and perimeter-overflow or glass-edge pools above that. No South African source prices the edge on its own, and none says whether VAT is included, so ask for the balance tank, the second pump circuit and the engineering as separate lines.
A vanishing edge spills over one wall, usually towards a view, into a catch basin below it. A full perimeter overflow — knife-edge or deck-level — spills over every side into a channel set flush with the deck, so the water sits level with the paving. The perimeter version has far more edge to keep level, around a closed loop where a low spot cannot be hidden; the single-sided version concentrates everything into one tall weir wall.
The edge stops, the water in transit drains into the catch basin and balance tank, and the tank sits full until the pump restarts — cosmetic in itself. The risk is what the system was built to handle: without a check valve, water can siphon back out of the pool, and a basin sized only for normal running can overflow and discharge water and chemicals. Ask about backflow prevention, and run the pumps on a timer with battery backup.
Yes. A spilling surface evaporates faster than a still one, and wind blows part of a thin sheet clear of the basin. That collides with Cape Town, where permanent regulations require a pool to be covered when not in use and prohibit an automatic top-up float valve fed from municipal drinking water — while a rim-flow pool is designed around a tank that needs topping up. We found nothing from the City or the industry addressing this pool type, so ask your municipality in writing first.
A slope makes a single-sided vanishing edge possible, because the water has to fall somewhere and the basin goes below the lip. Without a fall you can still build a deck-level perimeter overflow, which reads level with the paving rather than the horizon. On fibreglass: a moulded shell rarely gives a true rim-flow edge, because its rim is formed in the factory and its levelness set by the mould and the bedding, where a concrete wall is built and trimmed on site.
Featured builders
Builders with an award-winning pool of this type first, then by featured rank. Award counts shown are NSPI awards in rim-flow categories.
Bloubergstrand · Western Cape
Horizon Pools manufactures and installs fibreglass pool shells from Strand, serving Cape Town and the wider Western Cape. Relining of old concrete and fibreglass pools, plunge pools, hot tubs, water features, covers, nets, solar heating and mosaics all come off the same team.
Ballito · KwaZulu-Natal
Robust Pools has been building pools in Durban since 1988, working across eThekwini and the KwaZulu-Natal coast. Gunite and pre-formed fibreglass pools, rim-flow pools, renovations of older pools, and the paving and water features that go with them.
Ballito · KwaZulu-Natal
Kenny Matthews Pools builds, repairs and maintains pools along the KwaZulu-Natal north coast, from Salt Rock and Sheffield Beach through Ballito. Gunite construction for homes on tight coastal sites, and one of the most awarded builders in the country.
George · Western Cape
Island Pools has been building and restyling pools on the Garden Route for more than 25 years, working out of Knysna Industrial. Indoor and outdoor pools, saltwater and fibreglass builds, natural pools and spas, plus renovations of tired older pools.
Camps Bay · Western Cape
Radiant Pools has been building pools in Cape Town since 1972 and is still run by the same family, now in its third generation. The team takes on the awkward jobs: clifftop and rooftop pools, infinity edges and tight-access sites, as well as everyday gunite and fibreglass builds.
Gauteng
Curtis Pools has been building, repairing and maintaining pools around Johannesburg since 1973, now led by owner Russ Curtis. We build custom gunite pools with marbelite finishing, and handle shell-only rebuilds, enlargements, major repairs and commercial projects with real care for our clients.
Filter by province, budget, NSPI membership and award history.
Tell us about your site and we'll put you in front of builders who have finished rim-flow work you can go and look at. Mention the fall across your property — on this type it decides what the edge can do.
About this guide. PoolBuilders.co.za has been South Africa’s online swimming pool directory since 2004. Cost ranges on this page were researched from current South African builder and supplier pricing and last reviewed on 8 August 2026; they are published as ranges, never point prices, and are reviewed annually and whenever a featured builder tells us they are wrong. Every photograph is a real project from a builder listed in this directory, credited by name. Tell us something is wrong
